Scavenging for internal combustion engines



Sept. 8, 1936. I B. KAHN 2,053,338

SCAVENGING FOR INTERNAL COMBUSTION ENGINES Filed June 15,- 1954 5 Sheets-Sheet 1 INVENTOR Sept. 8, 1936. I-I

SCAVENGING FOR INTERNAL COMBUSTION ENGINES Filed June 13, 1 934 3 Sheets-Sheet 3 M239 #3351 hwmosu .54 m wad G kmsqtkm WE 3H6 8 5&5 5% has 2% 5% h Patented Sept. 8, 1936 UNiTED stares SCAVENGING FOR INTERNAL COMBUSTION A ENGINES Benjamin Kahn, New York, N. Y. Application June 13, 1934,'Serial No. 730,392

11 Claims.

This invention relates to two-cycle internal combustion engines of the single sleeve valve type. More particularly the invention relates to improvements in such engines-where carburetor induction of the combustible mixture is desired.

One of the main objects of the invention is to provide means whereby pureair scavenging of the cylinder is accomplished in an efiicient manner.

Another object is to prevent the diffusion be-. tween the outgoing burned gasesan'd the incoming combustible gas mixture.

Another object is to introduce a layer of pure air between the outgoing burned gases and the incoming combustible mixture.

A further object is to provide means whereby in the event of back firing of the engine, the flame is disbursed prior to any harmful effects.

Another object is to provide for supercharging in an engine of this character.

Other objects and advantages will appear in the following description wherein reference will be had to the accompanying drawings forming a part of this disclosure.

In the drawings:

' Figure 1 is a longitudinal section of an engine embodying the invention. 7

Figure 2 is a diagrammatic View showing the port timing in reference to the crank angle.

Figures 3, 4, 5, 6, '7, 8, 9 and 10 are similar diagrammatic viewsof a series of positions of the operating parts at various crank angle positions as indicated on figure 2. I

Figure 11 is a section taken on the line I|l| of Figure 1. Referring to Figure l the numeral [5 denotes a crankcase adapted to support a crankshaft l6. Secured to the crankcase is a cylinder I! having a head it. Adapted to operate within the cylinder is a sleeve it, which surrounds a piston 26 adapted to operate inside thesleeve. A connecting rod 2| is operably connected to the piston and to a crank pin 22 of the crankshaft. A second connecting rod is operably connected to the sleeve, and to a crank pin 23 on the same crank shaft. The sleeve driving crankpin 23 is in phased relation to the main crankpin 22.

As seen in Figure 3 to 10 the direction of rotation is counter-clockwise as indicated by the arrows. The sleeve crankpin 23 is phased ahead of the main crankpin 22 in the direction of rotation.

Air inlet ports 25 in the lower portion of the cylinder are arranged to extend substantially half way around the bore of the cylinder. Air inlet-controlling ports 26 in the sleeve are adapted to cooperate with the ports 25 in the cylinder. Gas inlet ports'2'i in the lower half of the cylinder, and substantially Within the same horizontal level of the ports 25, are arranged to extend substantially: half-way aroundthe other half of the cylinder bore. These ports 25 and 21 are'separ'ated against communication with each other by vertical portions 3 l of the cylinder forming partitions or sealing walls which contact'the sleeve ll at the circumferential extremities of the port. Gas inlet-controllingports 28 in" the sleeve are adapted to cooperate with'the ports 21. A sleeve port-bridge 3 labetween the adjacent air ports 26 and the gas ports 28, at opposite sides of the cylinder bore, are adapted to contact the portions 3| of the cylinder to effect a seal between the air and gas ports outside the sleeve. Exhaust ports 29 in the, cylinder are arranged to' surround the head end of the cylinder. Exhaust-controlling ports 36 in the sleeves are ad- 20 apted to cooperate with the exhaust ports 29. It will be noted that the heights of the stationary air and gas inlet ports in the cylinder are much greater than the heights of the corresponding and cooperating ports in the sleeve, respectively. 25

The piston top-face is adapted to cooperate withthe inlet ports -26'and'28 in the sleeve, to control the opening and closing off these ports. When the piston top-face is below the top edge of these ports in the sleeve, communication is establishedbetween the inlet ports 25 and 21 in the cylinder and the interior of the'sleeve via the ports 26 and 28 respectively. 1 1

Communication between the'interior of the sleeve and the exhaust ports 29 is established when the lower edge of the port 30 in the sleeve is below the upper edge of the ports 29 in the cylinder. e

When the ports are in the position shown in Figure 3 just after top dead center "of the piston the intake and exhaust ports are closed. The sleeve inlet ports 26 and 28 are completely above the cylinder inlet ports 25 and 21. The cylinder air and gas inlet ports 25 and 21 may extend higher than that shown, without opening the communication, so long as the lower edge of the piston extends below the lower edge of the sleeve inlet ports sufficiently to insure against leakage of the air or gas into the cylinder when the sleeve and piston are in the vicinity of top'dead center. I

The exhaust ports 30 in the sleeve, not shown iii-Figure 3, are completely confined in a recess formed betweenthe cylinder and the inreaching cylinder head I8 (Fig. l). a

PAT T OF'FICEL. I

Referring to the Figures 3 to 10, each comprises a diagrammatic illustration of the cylinder, sleeve and piston, and below each figure is an associated diagrammatic showing of the angular position of the cranks with respect to the parts shown directly above.

Beginning with the power impulse and continuing a working cycle, the charge is expanding in Figure 3. The next occurrence after the power impulse, is the opening of the exhaust ports. This does not begin however until the piston top has moved down considerably, to near the bottom of its stroke as shown in Figured. The exhaust ports in this figure are just at the point of opening. The air and gas inlet ports in the sleeve have moved about midway into the air and gas ports in the cylinder but are not in communication With the interior of the cylinder since the piston still covers the ports in the sleeve at this time. Upon further movement of the parts following Figure 4, the exhaust ports begin to open.

When the exhaust ports are about half way open, as seen in Figure 5, the air inlet ports are about to open.v These ports are shown at the point of initial opening, in Figure 5. It will be noted, in this position that the gas-inlet ports in the sleeve, are still closed by the piston covering these ports.

During the period between Figures 4 and 5, the burned charge leaves the interior of the cylinder under its own pressure. The residual burned gases remaining thereafter are at about atmospheric pressure. Upon further movement of the parts following their positions in Figure 5, these residual gases may be driven out by the incoming air under pressure thru the ports 25 and 26.

The pressure may be supplied by a suitable pump or impeller (not shown). Such devices are well known in the art. When the parts reach their position shown in Figure 6, the air inlet ports in the sleeve are about half way uncovered by the piston top. By this time the exhaust ports are almost fully open. This gives maximum egress to the residual burned charge. Some of the air may exhaust with and may follow the residual burned gases to insure a more complete scavenging of all of the burned charge.

When the parts reach their position shown in Figure 6, the gas-inlet ports in the sleeve are at the point of being opened by the piston top. Upon further movement thereafter, it will be noted that the exhaust ports will have become fully open and begin to close prior to their position in Figure 7.

During the period between Figures 6 and 7, the gas-inlet ports of the sleeve are opened and an over-rich gas mixture is permitted to enter under pressure by the use of a gas pump or impeller (not shown). It is preferable that the pressure of the incoming fresh gas charge be about equal to the pressure of the incoming air. Blowing-thru of the air and gas to their oppositely related open ports, is prevented by their being of substantially equal pressure and of greater pressure than that within the sleeve which is about atmospheric at the time. Furthermore, the inertia of the air column surging toward the exhaust at the top of the sleeve, urges the incoming air and gas to defleet upwardly, immediately after their entry to the interior of the sleeve. The clashing of the air and gas at equal pressures further aids in their upward travel and also aids in the intermixture of the two.

When the parts reach their position shown in Figure 7, the exhaust ports are still substantially wide open and are on the way to closing. The inlet ports are fully open by the piston being at its bottom dead center. The piston top is the controlling means for the ports in the sleeve. The gas ports in the cylinder are higher than their cooperating ports in the sleeve merely to accommodate the traveling oi the sleeve ports during operation. The opening of the gas ports is accomplished by the recession of the piston top with respect to the upper edge of these ports in the sleeve.

During the period between the Figures '7 and 8, the exhaust is closing. Inlet of air and gas still continues and at the time the parts reach their positions shown in Figure 8, both the air and gas inlets are still open whereas the exhaust is completely closed. The exhaust ports remain closed during the remainder of the cycle including the position shown in Figure 10 and Figure 3.

When the parts reach the position shown in Figure 8, the piston is on its way upward. The air and gas inlet ports are still open but they are being closed by the piston top which'at this time is about half way covering the bottom of the air gas inlet port. It will be noted in this figure that the gas inlet ports in the sleeve will be the first to close. This is due to their being disposed at a lower level than the air inlet ports in the sleeve. The upper edges of the gas inlet ports are at a lower level than the upper edges of the air inlet ports. These edges, as previously stated, in cooperation with the piston top determines the opening as well as closing of the communication of the interior of the sleeve at the proper time in the cycle;

During the period between the Figures 8 and 9, the gas inlet ports are closed and the air inlet ports are closing. At Figure 9 the air inlet ports are still open and the gas inlet ports are just closed. The air inlet ports remain open until the parts reach the position shown in Figure 10 where the 'air inlet ports are just closed by the piston top. The exhaust ports being closed at this time will cause the charge to be compressed on the further upward movement of the piston.

Between the Figures 10 and 3 the charge is ignited and the power stroke begins at about Figure 3 which completes the cycle of the operation.

It is to be particularly noted that with such parts as illustrated the controlling or top edge of the inlet ports 26 in the sleeve are higher or stepped with respect to the controlling or top edges of the gas inlet ports 28 in the sleeve. These stepped ports, in cooperating with a flat piston top, effect the opening of the air inlet ports prior to the opening of the gas inlet ports. It is obvious that in the event a stepped piston top is employed to control the opening and closing of the sleeve inlet ports 26 and 28, and the steps of the piston is equal to the difference be tween the controlling edges of the ports 26 and 28, the upper edges of the air, and gas sleeve ports 26 and 28 may be arranged at the same transverse level without changing the function as when employing stepped ports in the sleeve, i. e. opening of the air ports prior to the opening of the gas ports. It will be seen that when the air inlet ports are first to open on the downward stroke of the piston, they will be the last to close on theupward stroke.

It will be further. noted that when the piston top is moved below the top edge of the airinlet ports (between Figures and 6) pure air only is permitted to enter the interior of the sleeve. Gas is prevented from entering until such time as the piston top moves below the top edge of the gas intake ports in'the sleeve. While air only is entering, there is no communication between the air inlet ports and the gas inlet ports. This prevents diffusion of scavenging air (which scavenging air, later, may bepermitted to escape thru the exhaust) with any fresh gas. 7

When the gas inlet ports are opened by the piston top, diffusion takes place between the incoming air and the gas which is desirable as it constitutes the combustible mixture. Loss of this combustible mixture is prevent-ed since a layer of air precedes this combustible mixture on its way toward the exhaust ports; and since this layer of air, by propertiming of the closing of the exhaust ports may be severed, retention in the interior of the sleeve of all of the combustible mix ture is accomplished.

The air ports being the last to close will permit a layer of pure air to follow the combustible mixture into the interior of the sleeve. This layer of air serves to crowd the combustible mixture up into the vicinity of the igniter, which in a sleeve valve engine is usually in a cavity in the head.

The closingof the air ports last, serves another important function in a carburetor induction two cycle engine, i. e. it prevents the flame travel into the gas chamber in the event the engine back fires. During back fire of the engine the flame is permitted toenter the air chamber and expand its heat and energy therein prior to the opening of the gas ports.

This results in fouling of the air in the air inlet chamber only and does not foul the next on-coming gas charge; Fouling of the air does not greatly curtail the following charging and ex- 7 plosion, whereas fouling of the gas results in further tendency to misfireand backfire especially at low speeds.

It will be particularly noted that during the period when the air ports only are open, (between Figures 5 and 6 and between 9 and 10) the gas ports are completely closed and there is no inter-communication between the gas and air inlet ports in the cylinder.

It will be noted that since the piston and the sleeve are operated with crankmotions that the resulting motion of the pistons and the sleeves are of the substantially simple harmonic character. That is, their accelerated motions are smooth and regularly increasing. This is pointed out in contrast to the operations of such elements where cams or other linkage is used to operate these elements. A crank motion injects no impact loads when the reciprocating parts change their direction. Whereas cams and other linkages cause no simple harmonic motion to their reciprocating elements,- and result in impact somewhere in the train when the reciprocating elements change their direction or when their velocities are too suddenly increased or decreased. The cranks have the characteristics of gradually increasing or decreasing the velocities of the reciprocating elements to prevent impacts.

Whereas in the drawing only one air inlet port and one horizontally adjacent gas inlet port is shown to completely circumscribe the cylinder, it is to be understood that there may be a plurality alternating air and gas ports circumscribing the cylinder.

It will be noted in Figure 2 that the exhaust ports are first toopen followed by the opening of the inlet ports. Theexhaust ports are closed prior to the closing of the inlet ports. The opening interval of the inlet ports is shorter than the closing interval of the inlet ports thereby providing for supercharging of the cylinder. In detail, first the burned charge is permitted to exhaust by the opening of the exhaust ports and the pressure in the cylinder is considerably reduced, air under pressure is then permitted to enter the bottom of the cylinder to drive out the remainder of the burned charge. Some of the air may be permitted to pass thru the exhaust ports to insure a complete scavenging. Gas is then permitted to enter with the air and before any of it escapes thru the exhaust ports these exhaust ports are closed. The gas ports are then closed leaving only the air ports open and air under pressure is last fed to the cylinder. Supercharging is thus made possible by the closing of the exhaust ports prior to the closing of the intake ports.

Having thus described one embodiment of the invention what is desired to claim is:-

I. In a two-stroke cycle gas-induction internal combustion engine, the combination including a cylinder having exhaust ports at the top, independent air and gas inlet ports at the bottom thereof, a single sleeve operating in the cylinder adapted to control the exhaust ports, ports in the lower portion of the sleeve cooperating with inlet ports in the cylinder, a piston operating in the sleeve for controlling the inlet ports in the sleeve,

a crankshaft operated by said piston, and means operably connected to the crankshaft for reciprocating the sleeve in a substantially simple harmonic motion, said sleeve being arranged to operate inphased relation to the piston whereby the opening interval of the inlet ports is less than the closing interval. i

2. In a two-stroke cycle gas-induction internal combustion engine of the straight-thru scavenging type, the combination including a cylinder with exhaust ports at the top thereof, a single sleeve operating in the cylinder for controlling the exhaust ports, independent air and gas inlet ports of unequal height in the lower end of the cylinder, a sleeve having ports ccoperable with said inlet ports, a piston operable in the sleeve for establishing communication of the air inlet ports to the interior of the sleeve prior to establishing communication of the gas inlet ports to the interior of the sleeve, and means whereby the piston and sleeve are operated in a substantially simple harmonic motion and in phased relation to each other, whereby the interval of opening of the inlet ports is less than the closing interval.

3. In a two-stroke cycle gas-induction internal combustion engine of the straight-thru scavenging type the combination of a cylinder with exhaust ports at top and inlet ports at the bottomthereof, a single sleeve operating in the cylinder and having ports cooperating with the ports in the cylinder, a piston operating in the sleeve and cooperating with the inlet ports in the sleeve to admit pure air to the interior of the sleeve and to admit a gas mixture to the interior of the sleeve, and means for delaying the admission of the gas mixture, said sleeve and piston operating in substantially simple harmonic motions and having fixed phased relation to each other.

4. In a two-stroke cycle gas-induction internal combustion engine of the straight-thru scavenging and supercharging type the combination of a cylinder with exhaust ports at top and air and gas inlet ports at the bottom thereof, a single sleeve operating in the cylinder having air and gas ports cooperating with the ports in the cylinder, a piston operating in the sleeve and cooperating with the inlet ports in the sleeve to admit pure air to the interior of the sleeve and to admit a gas mixture to the interior of the sleeve, and means for delaying the admission of the gas mixture during the power stroke until after the entrance of air and delaying the closing of the air inlet ports during the compression stroke, until after the admission of gas, said piston and sleeve operating in cyclically fixed phased relation.

5. In a twoestroke cycle gas-induction internal combustion engine of the straight-thru scavenging and supercharging type the combination of a cylinder with exhaust ports at the top and inlet ports at the bottom thereof; a single sleeve operating in the cylinder having ports cooperating with the ports in the cylinder, a piston operating in the sleeve and cooperating with the inlet ports and the sleeve to admit a gas mixture into the interior thereof and toadmit pure air prior to, during and after the admission of the gas mixture, and means whereby said piston and sleeve operate cyclically fixed phased relation.

6. In a two-stroke cycle gas-induction internal combustion engine of the straight-thruscavenging type the combination of a cylinder having exhaust ports at the top andiindependent air gas inlet ports at the bottom thereof, and a single sleeve having ports at the top thereof for controlling the exhaust ports, inlet ports in the lower end of the sleeve cooperating with the air inlet ports in the cylinder to admit pure air, inlet ports in the lower end of the sleeve cooperating with the gas inlet ports in cylinder to admit a gas mixture, and a piston operating in the sleeve and cooperating with the inlet ports therein, said ports in the sleeve being in staggered relationship with respect to the piston top and being in communication with the ports in the cylinder during the opening of the sleeve ports by the piston top, said piston and sleeve operating in cyclically fixed phased relation.

7. A gas-induction sleeve valve engine having a cylinder, a single sleeve valve means having inlet ports at one extremity and exhaust ports at the other extremity thereof and associated with the cylinder for controlling the charging of fluid to the interior of the sleeve, means asso-. ciated with said sleeve valve whereby pure air is admitted to the interior of the cylinder and whereby a gas mixture is admitted intermediate the pure air, and means whereby the opening interval of the air and gas admitting means is shorter than the closing interval.

8. In a gas-induction sleeve valve engine of the supercharging type the combination of a cylinder, ports in the cylinder, a sleeve valve means having inlet ports at one extremity and exhaust ports at the other, said ports respectively associated with the ports in cylinder, and means associated with said sleeve valve means including an inlet port-controlling piston in the sleeve for admitting first pure air, then pure air and a gas mixture, and last pure air to the interior of the sleeve during the period including the end of the power stroke and the beginning of the compression stroke, said piston and sleeve operating in substantially simple harmonic moions.

9. An internal combustion engine including a crankcase, a cylinder on the crankcase having exhaust ports at the top and intake ports at the bottom, a crankshaft in the crankcase, a sleeve in the cylinder having intake ports registrable with the ports in the cylinder, said intake ports in the cylinder comprising independent air and gas ports, said inlet ports in the sleeve comprising air ports and gas ports, said air ports being of greater height than the gas ports, an inlet port-controlling piston operative in the sleeve having a substantially simple harmonic motion whereby the air intake ports are first to open and last to close, and. means associated with the crankshaft for imparting a substantially simple harmonic motion to the sleeve, said sleeve and piston being arranged to reciprocate in fixed phase relationship, whereby the opening interval of the inlet ports is shorter than the closing interval.

10. In a two-stroke cycle gas-induction internal combustion engine the combination including a cylinder having inlet and exhaust ports, a sleeve in the cylinder having a substantially simple harmonic motion, a piston in the sleeve having a substantially simple harmonic motion, said inlet ports in the cylinder comprising independent airand gas ports, ports in the sleeve registrable with the gas ports in the cylinder, and air ports in the sleeve of greater height than the gas ports in the sleeve and registrable with the air ports in the cylinder, said piston in the sleeve adapted to control the opening and closing of the air and gas ports to the interior of the sleeve whereby the opening interval is of less duration than the closing interval.

11. In a sleeve valve engine the combination of a cylinder with exhaust ports at the top thereof, separate air and gas inlet ports at the bottom thereof, a sleeve having exhaust ports cooperable with the cylinder exhaust ports, air and gas ports in the sleeve cooperable with the cylinder air and gas ports, said air ports in the cylinder being of greater height and extending above the gas ports in the cylinder, said sleeve air ports being of greater height and extending above the sleeve gas ports, a piston in the sleeve controlling the inlet of air and gas to the interior of the sleeve, means for directing the motion of the piston substantially simple harmonic, and means for directing the motion of the sleeve in cyclically fixed phased relation to the motion of the piston.

BENJAMIN KAHN. 

